The invention relates to a method for blow molding and for filling containers in which a preform is initially thermally conditioned and subsequently shaped within a blow mold by the influence of blowing pressure into the container, and in which the blow molded containers are positioned by a support element at least along a portion of their conveying path, wherein the support element is supported by a rotating transfer wheel, and wherein the transfer wheel constitutes at least a portion of a coupling between a blow molding module for the manufacture of containers and a filling module for filling containers.
Moreover, the invention relates to an apparatus for blow molding and for filling containers which includes at least one blow molding station with a blow mold and at least one support element for positioning blow molded containers along a transport path, wherein the support element is supported by a rotating transfer wheel, and wherein the transfer wheel constitutes at least a portion of a coupling between a blow molding module for the manufacture of containers and a filling module for filling the containers.
When containers are shaped by the influence of blowing pressure, preforms of a thermoplastic material, for example, preforms of PET (polyethylene terephthalate), are supplied within a blow molding machine to different processing stations. Such a blow molding station typically includes a heating device and a blow molding device in whose area the previously thermally conditioned preform is expanded into a container by a biaxial orientation. The expansion takes place by means of compressed air which is introduced into the preform which is to be expanded. The sequence of such an expansion of the preform with respect to production technology is explained in DE-OS 43 40 291. The introduction of gas which is under the influence of pressure mentioned above further comprises the introduction of compressed gas into the developing container bubble as well as the introduction of compressed gas into the preform at the beginning of the blow molding process.
The basic construction of a blow molding station for shaping containers is described in DE-OS 42 12 583. Possibilities for thermally conditioning the preforms are explained in DE-OS 23 52 926.
Within the apparatus for blow molding, the preforms as well as the blow molded containers can be transported by means of different manipulating devices. Particularly useful has been found the use of transport mandrels onto which the preforms are placed. However, the preforms can also be manipulated by other support devices. The use of gripping tongs for manipulating preforms and the use of spreading mandrels, which for providing support can be inserted into an opening area of the preform, are also among the available constructions.
A manipulation of containers with the use of transfer wheels is described, for example, in DE-OS 199 06 438 in an arrangement of a transfer wheel between a blow molding wheel and a discharge station.
The manipulation of the preforms already described above takes place, on the one hand, in the so called two-stage methods in which the preforms are initially manufactured in a blow molding method, are subsequently subjected to intermediate storage, and are only later conditioned with respect to their temperature and are in this state blown up into a container. On the other hand, an application of the so called single-stage method in which the preforms are suitably thermally conditioned directly after their manufacture according to blow molding technology and a sufficient solidification and are subsequently expanded.
Different embodiments are known in the art with respect to the blow molding stations used. In blow molding stations which are arranged on rotating transport wheels, a book-like opening capability of the mold supports can be found frequently. However, it is also possible to use mold supports which are slidable relative to each other or are guided in different ways. In stationary blow molding stations which are particularly suitable for receiving several cavities for the shaping of containers, typically plates which are arranged parallel relative to each other are used as mold supports.
For the manipulation of the preforms and the manipulation of the blow molded containers, frequently so called transfer wheels are used within the blow molding machine, wherein the transfer wheels are equipped with support elements for the preforms or bottles. In this case, the support elements may act either directly on the preforms or bottles, or may convey separate transport elements which, in turn, directly support the preforms or bottles. For reinforcing the transfer procedures, the support elements are typically mounted so as to be pivotable relative to the transfer wheel. In addition, frequently also a telescoping capability is realized. For predetermining the positions of the support elements, cam controls are used. For this purpose, the support elements are guided with cam rollers past cams which are arranged so as to be stationary.
The blow molding module already mentioned above comprises essentially a rotatable blow molding wheel with blow molding stations; the filling module comprises essentially a rotatable filling wheel with filling stations.
Rotating transfer wheels with support elements are also used in so called block machines to couple a blow molding module to a filling module. In such blocked arrangements, a problem resides in the fact that the filling module predetermines a maximum filling quantity per unit of time. For example, if a blow molding machine for manufacturing containers having a volume of 0.5 liters is coupled to a filling module and both modules are selected in accordance with their productivity while taking into consideration these border conditions, it is not easily possible to retrofit the blow molding machine for the production of containers having a volume of 1 liter and to have the filling module fill these larger containers with an equal number of containers per unit of time.
Also, in this example, it is not easily possible to just have the blow molding wheel of the blow molding machine travel more slowly, because in cam-controlled blow molding machines frequently process-technological parameters, for example, the stretching speed, are derived from the rotation of the blow molding wheel and cannot be easily varied. Therefore, an adjustment of the productivity of the blow molding module and of the filling module relative to each other poses difficulties when processing containers having volumes which differ from each other.